Advances in biotechnology witnessed in recent years have been accompanied by increasing demand for localized process of cells and the like, involving making a hole in a cell membrane or wall, and removing the nucleus from the cell, or introducing DNA or other nucleic acid substance into the cell. Methods employing a number of localized process techniques (hereinafter sometimes referred to as “localized ablation methods”), such as contact process techniques using a probe, such as an electric scalpel or the like, or non-contact ablation techniques employing lasers or the like, are widely known. In particular, as a contact process technique using an electric scalpel, there has recently been proposed a technique for keeping the cauterization surface to one on the order of several micrometers, thereby minimizing the thermal invasion area and improving the resolution performance (see Non-patent Document 1).
Additionally, in the area of laser process, there have been notable breakthroughs in femtosecond lasers, and techniques for performing cell process (see Non-patent Document 2) and laser process techniques that minimize generation of bubbles in the liquid phase have been recently proposed.
However, in conventional contact process techniques employing a probe such as an electric scalpel, there was a tendency for the target to be burned away due to Joule heat generated by continuous high frequencies, resulting in significant roughness at the incision face and in surrounding tissue being significantly affected by thermal invasion due to heat (Problem 1); and rejoining and regeneration were difficult, due to denaturation of proteins and/or fragmentation of amide bonds (Problem 2). Moreover, with continuous process, adsorption onto the probe of cut proteins and/or adsorption of bubbles generated by heat resulted in the problem of marked degradation of the observation environment at the incision face, making high-resolution process difficult (Problem 3).
In non-contact process techniques employing lasers such as femtosecond lasers and the like as well, tissue surrounding the incision face was affected by localized bombardment with high-density energy, and particularly during process of a target in the liquid phase, generation of bubbles and the like due to heat generated during process made continuous process difficult (Problem 4). Another problem encountered during process of a target in the liquid phase with a laser such as femtosecond laser was difficulty in accessing the process target (Problem 5).
Meanwhile, electroporation, sonoporation techniques employing ultrasound, particle gun methods, and the like are widely known as localized physical injection techniques (injection methods) for introducing nucleic acid substances or the like into cells or the like. Electroporation is a technique in which an electrical pulse is imparted to a cell or the like, thus raising the cell membrane permeability in order to carry out injection; a technique for injection into a thin pliable cell membrane such as lipid bilayer membrane has been proposed (see Non-patent Document 3). In the area of sonoporation techniques employing ultrasound, it has been proposed to bombard bubbles with ultrasound to carry out injection by generating cavitation in a wide range of bubbles (see Non-patent Document 4). Additionally, the particle gun method is a technique involving depositing a substance to be introduced onto a particle, which is then physically shot into the target.
However, in conventional electroporation techniques, depending on the electrical field strength, there are limits as to how much the permeability of the cell membrane can be improved, making it difficult to inject into targets having stiff cell membranes or cell walls, instead of pliable lipid bilayer membranes (Problem 6); and due to restrictions regarding electrode placement and the like, localized injection at the intended site was difficult. Moreover, in sonoporation techniques employing ultrasound, it was difficult to focus the ultrasound, making it difficult to generate localized cavitation of bubbles and increase the resolution (Problem 7).
In injection methods that rely on the particle gun method as well, the problem of low efficiency of introduction, due to separation of the substance deposited on the particle surface occurring when the particle is shot in, was encountered (Problem 8). Additionally, the electroporation, sonoporation, and particle gun methods consume large amounts of substances for injection, making injection of costly substances difficult (Problem 9).
Plasmas are known to be able to contribute to killing malignant cells and healing biological tissue. However, in conventional plasma techniques, it was difficult to bring about a state that would generate a plasma in solution, and while a procedure of first generating a plasma a gas in proximity to the electrodes, and then using the generated plasma to generate bubbles including the plasma in solution, was adopted, the plasma state could not be sustained for an extended period, and it was moreover difficult to move the bubbles while maintaining a plasma state (Problem 10, see Non-patent Documents 5, 6).